Deburring is a problem not only in the production of innumerable items of metal, but also in the production of items of other materials, for example items of plastic, where the items can have flashed edges or projections.
When the deburring of items of metal is involved, it is often a great advantage if a uniform chamfer can be produced on the contour of the item.
In addition to the manual deburring of the individual items by a worker using a file, there are also various technologies for deburring during mass production, such as electrolytic deburring and vibration in an abrasive material, grinding, sandblasting, rinsing with various materials and high-pressure flushing with abrasive additives.
The above-mentioned methods of deburring during mass production have a number of disadvantages, of which the following can be mentioned:
1)The items must be separated from the abrasive, PA1 2)The items must be cleaned of dust/liquids, PA1 3)The items can damage one another by mutual contact, PA1 4)The items are heated by the deburring process, PA1 5)The processes are slow, PA1 6)There often occurs a so-called folding-back of the burrs or flash, and PA1 7)The result of the deburring varies and depends on the shape of the items, for example at a circular hole, where different chamfer radii can appear along the edge of the hole.
From U.S. Pat. No. 5,468,173 there is known a machine for the deburring of metal items, said machine comprising two sets of deburring heads each with four deburring rollers provided with abrasive leaves which extend radially outwards from a retaining cylinder. All of the deburring rollers are rotated and turned in the same direction across the item which is to be deburred.
However, this machine is not suitable for deburring in corners and narrow passages, the reason being that the breadth of the deburring leaves sets a limit for the breadth of the opening which can be processed.
Furthermore, the relative stiffness of the leaves sets a limit for their possibility of adjusting themselves to different contours and edges.
Despite the many different methods and machines for deburring, many deburring tasks must still be carried out manually, in that this is made necessary by the above-mentioned disadvantages and the demand concerning uniform chamfer radii along the multifarious contours of the items.
Manual deburring is, however, time-consuming and therefore costly in mass production. Moreover, scratches often appear in the deburred edges, which scratches can contribute towards the formation of cracks, which in turn can lead to fractures in the items.
In the aviation industry, there thus exits a problem in the manufacture, for example, of ribs for aircraft wings or similar items. These ribs are made of a large metal item which is machined to the precise configuration. When the ribs are thus brought down to their final dimensions, the burrs which result from the machining must be removed during simultaneous chamfering with quite precise chamfer radii of the edges at holes and outer edges. These chamfers shall not only have a certain radius, but the chamfers must also be completely free of scratches or marks after the deburring, in that such scratches or marks can lead to the formation of cracks as a consequence of vibrations in the finished ribs when they are mounted in an aircraft wing or a similar place.
The Technical Problem Which Needs to be Solved
There is thus a need for being able to carry out the deburring of metal items without this giving rise to scratches or cracks in the deburred edges of the items, in that at the same time as the deburring there shall also be produced chamfers with uniform radii on the contours of the items.
Where the items are to he given subsequent surface treatment, it is desirable that the deburring is effected with uniform contours, in that it is hereby ensured that the surface coating, such as paint, can be applied in a layer of the desired thickness.
The New Technique
It is therefore the object of the present invention to provide a method for the deburring of metal items which are encumbered with sharp edges or burrs after punching, clipping, moulding and/or machining operations.
This object is achieved with a method of the kind disclosed in the preamble, said method according to the invention being characterized by the items being fed in under a deburring tool which sweeps the surface of the items, said deburring tool comprising a number of deburring rollers which are comprised of deburring disks, each of which consists of a circularly-cut piece of abrasive material provided with radial slits in the formation of a large number of abrasive fingers, said deburring disks each being secured to its own spindle axle which extends radially outwards from a drive, said deburring rollers rotating in opposite directions in pairs around the spindle axles, and also being turned around a turning axle which extends at right-angles to the spindle axles, in that the deburring rollers are also moved in a reciprocating manner parallel with the surface of the items in a direction transversely to the feeding direction of the items.
If the items have at least a partly plane underside, it is also advantageous to feed the items on a vacuum surface which can secure the items during their forward feeding under the deburring tool, in that the movement of the air serves to cool the surface of the items.
The Technical Effect
It has surprisingly proved that the effect of the deburring and the processing is concentrated on the edges of the items where the burrs are normally left remaining or are folded over, also that the items are not influenced by process heat, in that the deburring disks create circulation for cooling of the items' surfaces, also that the deburring does not call for subsequent cleaning since the process is effected in a dry manner, and that even on complex items there is achieved a uniform, similar chamfer radius on all contours, regardless of whether these contours extend on outer edges of the items or on edges of holes of different shapes.
Those areas on the items surfaces which lie between the mentioned edges shall, on the other hand, be ground even and smooth without any significant removal of material.
The fingers on the deburring disks provide a great flexibility, which allows the fingers to penetrate some distance down into recesses and holes in the items, so that the chamfering on the contours can achieve the intended radius. Similarly, the relatively narrow fingers can penetrate down into narrow openings and passages and enable these to be processed.
Moreover, the effect of the oppositely-rotating deburring tools is that the item is not influenced in one and the same direction, which means that the holding power on the plane does not need to be particularly great. This results in great assurance for a precise deburring and shape.
The effect of placing the items on a vacuum plane is therefore that they are held in a secure manner during the processing and, in addition, that a cooling effect is provided on the surface of the items during the deburring.
With smooth items, it has hitherto been difficult in a subsequent surface treatment in the form of painting/lacquering to get the treatment material to adhere to the surface of the items.
When the items are deburred/frazed by the method according to the invention, it has proved that the surface treatment material achieves a surprisingly good adherence to the surface of the items.
Therefore, the method according to the invention can with advantage be used for the deburring of ribs on wings for aircraft while simultaneously chamfering various edges on the ribs, and plate items can be processed in a similar manner.